1. Field of the Invention
This invention relates to the transmission of communication signals over the AC power line. More particularly, this invention relates to the improvement in signal transmission efficiency through the detection and selection of a transmission frequency selected to avoid power line noise and the like.
2. Description of the Related Art
A variety of techniques have been proposed to address the problem of power line noise, mismatches, and signal attenuation. Typically such techniques involve filtering, signal power amplification and/or transmission over multiple frequencies. These prior techniques all suffer from transmission inefficiency.
For general background material the reader is directed to the following U.S. patents each of which is incorporated in its entirety for the material contained therein.
U.S. Pat. No. 4,668,934 describes a receiver apparatus for three-phase power line carrier communications, in which each phase conductor is coupled to a common point that is connected in signal communication with an input to a receiver.
U.S. Pat. No. 4,715,045 describes a system protocol for the composite shift key communication of binary signals in which a transmitting transceiver transmits a first summed signal having a first qualifying signal at a qualifying signal frequency as one of the summed signal components only when a binary signal is desired to be transmitted.
U.S. Pat. No. 4,912,553 describes a wideband video system that transmits and receives video signals through a ground line of a power distribution network.
U.S. Pat. No. 5,195,098 describes a binary data error correction method and apparatus, which permits the correction of double errors using a Hamming code and a parity bit.
U.S. Pat. No. 5,210,518 describes an apparatus and method for reducing errors in data caused by noise in a power line communication system.
U.S. Pat. No. 5,260,974 describes an apparatus, which uses a carrier detection threshold level for detecting a carrier signal modulated with binary data.
U.S. Pat. No. 5,264,823 describes a power line communication system wherein data is transmitted on a power line as a momentary interruption of the power at or near the zero crossing of the current.
U.S. Pat. No. 5,289,476 describes a power line communication-apparatus wherein transmission mode information is encoded into each data packet while maintaining immunity from single bit errors.
U.S. Pat. No. 5,289,498 describes a method and means for recovering data in a spread spectrum communications system using adaptive data recovery techniques.
U.S. Pat. No. 5,355,114 describes a power line communication apparatus where data is redundantly transmitted on a first and a second carrier where the carriers are separated by a predetermined number of Hz.
U.S. Pat. No. 5,377,227 describes a method and means for recovering data in a spread spectrum communications system, that includes a method and means for providing a sync window time period.
U.S. Pat. No. 5,559,377 describes an apparatus for electrical line communication that includes a coupler at each of two or more locations along a pair of lines, the coupler having capacitive circuits serially connected with an air-core transformer.
U.S. Pat. No. 5,625,863 describes a cable television/video distribution and selection system for distributing video signals throughout a home or building over in-wall electrical wiring.
U.S. Pat. No. 5,705,974 describes a coupling circuit for a power line communications system for coupling information signals from a transmitter unit to a power line and for coupling information signals from the power line to a receiver unit.
U.S. Pat. No. 5,717,685 describes an apparatus for electrical line communication that includes a coupler at each of two or more locations along a pair of lines, the coupler having capacitive circuits serially connected with an air-core transformer.
U.S. Pat. No. 5,805,053 describes an electrical appliance in which a power line adapter unit is embodied by which information signals are conducted to and from a power line from and to the appliance along the same connection to the power line by which the appliance is powered.
U.S. Pat. No. 5,818,127 describes an apparatus for electrical line communications using FM video modulation that includes FM video modulation circuits and an impedance matching coupler at each of two or more locations along a pair of lines.
U.S. Pat. No. 5,841,807 describes a spread spectrum data communicator, which has a plurality of transmitters for uni-directionally simultaneously transmitting, through a transmission medium to a single receiver, a plurality of data streams.
It is desirable to provide a method and system for the detection of signal mismatches and reflections on an AC power line being used for communications. In particular, it is desirable to provide a method and system, which compensates for signal attenuation on an AC power line by selecting a frequency channel and adjusting the signal power to a level needed for reliable transmission of the signal over the power line.
Therefore, it is the general object of this invention to provide a method and system for detecting the signal attenuation on an AC power line being used for a communication channel.
It is a further object of this invention to provide a method and system, which can detect the noise on a power line at a given frequency.
It is a still further object of this invention to provide a method and system for determining the signal power needed for a reliable transmission link.
Another object of this invention is to provide a method and system for selecting a channel frequency having reduced noise.
A further object of this invention is to provide a method and system for selecting a channel frequency having reduced attenuation.
A still further object of this invention is to provide a method and system for improving the transmission reliability in an AC power line communication channel.
Still another object of this invention is to provide a method and system for making an AC power line communication channel RF spectrum efficient.
Another object of this invention is to provide a method and system for improving the quality of signal transmission over an AC power line that is compatible with either analog or digital transmission techniques.
These and other objects of this invention are achieved by the method and system herein described and are readily apparent to those of ordinary skill in the art upon careful review of the following drawings, detailed description and claims.